1. Field of the Invention
This application concerns a mileage recording odometer device with a plurality of digit wheels mounted in close side by side relationship on a shaft. Each digit wheel has a hub portion encircling the shaft and an outer rim portion bearing mileage indica thereon. Several spokes connect the hub and the rim portions and are formed integrally with the hub and rim. The improvement resides in the configuration of the spokes whose cross section of a spoke progressively decreases toward the midportion so that it the spoke is frangible in resonse to a significant axially directed prying force on the rim portion of the wheel.
2. Description of Related Art
There have been earlier attempts to prevent odometer tampering. The U.S. Pat. No. 3,949,201 utilizes an obliterating means to destroy the mileage indica on the outer surface of the wheels whenever the a wheel is rotated in a reverse direction to decrease mileage indication. In U.S. Pat. No. 3,636,320, a drive or input mechanism operates only to advance the indica wheels and resists reverse rotation of the wheels. Likewise, U.S. Pat. No. 3,785,551 provides a transfer mechanism between the wheels to prevents their reverse rotation.
The U.S. Pat. No. 3,482,773 discloses a transfer mechanism between each wheel including a strap member secured in one position during normal odometer operation. The strap is designed to break or become unsecured when an attempt is made to rotate the wheel in a reverse direction by "picking."
The U.S. Pat. No. 4,284,882 discloses an odometer having a transfer mechanism between odomeeeter wheels mounted on a shaft having a weakened portion adapted to break when an attempt is made to rotate the wheels in a reverse direction. Likewise, the U.S. Pat. No. 4,267,438 discloses an odometer with wheels mounted on a shaft having notches therein to weaken the shaft so that the shaft breaks if significant prying is attempted. Also, the wheels include radially extending grooves designed to cause the wheel to break in the radial direction or into sectors upon application of a prying force.